/**
 * @(#)Assert.java
 *
 * Copyright (c) 2010 wstuo. All Rights Reserved.
 */
package com.wstuo.common.util;

import java.util.Collection;
import java.util.Map;

/**
 * Assertion utility class that assists in validating arguments. Useful for
 * identifying programmer errors early and clearly at runtime.
 * 
 * <p>
 * For example, if the contract of a public method states it does not allow
 * <code>null</code> arguments, Assert can be used to validate that contract.
 * Doing this clearly indicates a contract violation when it occurs and protects
 * the class's invariants.
 * 
 * <p>
 * Typically used to validate method arguments rather than configuration
 * properties, to check for cases that are usually programmer errors rather than
 * configuration errors. In contrast to config initialization code, there is
 * usally no point in falling back to defaults in such methods.
 * 
 * <p>
 * This class is similar to JUnit's assertion library. If an argument value is
 * deemed invalid, an {@link IllegalArgumentException} is thrown (typically).
 * For example:
 * 
 * <pre class="code">
 * Assert.notNull(clazz, &quot;The class must not be null&quot;);
 * Assert.isTrue(i &gt; 0, &quot;The value must be greater than zero&quot;);
 * </pre>
 * 
 * Mainly for internal use within the framework; consider Jakarta's Commons Lang
 * >= 2.0 for a more comprehensive suite of assertion utilities.
 * 
 * @version 1.00 2007-4-23
 * @author <a href="mailto:wstuowang@msn.com">wstuo Wang</a>
 */
@SuppressWarnings("unchecked")
public abstract class Assert {

	/**
	 * Assert a boolean expression, throwing
	 * <code>IllegalArgumentException</code> if the test result is
	 * <code>false</code>.
	 * 
	 * <pre class="code">
	 * Assert.isTrue(i &gt; 0, &quot;The value must be greater than zero&quot;);
	 * </pre>
	 * 
	 * @param expression
	 *            a boolean expression
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @throws IllegalArgumentException
	 *             if expression is <code>false</code>
	 */
	public static void isTrue(boolean expression, String message) {

		if (!expression) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert a boolean expression, throwing
	 * <code>IllegalArgumentException</code> if the test result is
	 * <code>false</code>.
	 * 
	 * <pre class="code">
	 * Assert.isTrue(i &gt; 0);
	 * </pre>
	 * 
	 * @param expression
	 *            a boolean expression
	 * @throws IllegalArgumentException
	 *             if expression is <code>false</code>
	 */
	public static void isTrue(boolean expression) {

		isTrue(expression, "[Assertion failed] - this expression must be true");
	}

	/**
	 * Assert that an object is <code>null</code> .
	 * 
	 * <pre class="code">
	 * Assert.isNull(value, &quot;The value must be null&quot;);
	 * </pre>
	 * 
	 * @param object
	 *            the object to check
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @throws IllegalArgumentException
	 *             if the object is not <code>null</code>
	 */
	public static void isNull(Object object, String message) {

		if (object != null) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that an object is <code>null</code> .
	 * 
	 * <pre class="code">
	 * Assert.isNull(value);
	 * </pre>
	 * 
	 * @param object
	 *            the object to check
	 * @throws IllegalArgumentException
	 *             if the object is not <code>null</code>
	 */
	public static void isNull(Object object) {

		isNull(object, "[Assertion failed] - the object argument must be null");
	}

	/**
	 * Assert that an object is not <code>null</code> .
	 * 
	 * <pre class="code">
	 * Assert.notNull(clazz, &quot;The class must not be null&quot;);
	 * </pre>
	 * 
	 * @param object
	 *            the object to check
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @throws IllegalArgumentException
	 *             if the object is <code>null</code>
	 */
	public static void notNull(Object object, String message) {

		if (object == null) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that an object is not <code>null</code> .
	 * 
	 * <pre class="code">
	 * Assert.notNull(clazz);
	 * </pre>
	 * 
	 * @param object
	 *            the object to check
	 * @throws IllegalArgumentException
	 *             if the object is <code>null</code>
	 */
	public static void notNull(Object object) {

		notNull(object,
				"[Assertion failed] - this argument is required; it must not null");
	}

	/**
	 * Assert that a string is not empty; that is, it must not be
	 * <code>null</code> and not empty.
	 * 
	 * <pre class="code">
	 * Assert.hasLength(name, &quot;Name must not be empty&quot;);
	 * </pre>
	 * 
	 * @param text
	 *            the string to check
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @see StringUtils#hasLength
	 */
	public static void hasLength(String text, String message) {

		if (!StringUtils.hasLength(text)) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that a string is not empty; that is, it must not be
	 * <code>null</code> and not empty.
	 * 
	 * <pre class="code">
	 * Assert.hasLength(name);
	 * </pre>
	 * 
	 * @param text
	 *            the string to check
	 * @see StringUtils#hasLength
	 */
	public static void hasLength(String text) {

		hasLength(
				text,
				"[Assertion failed] - this String argument must have length; it must not be <code>null</code> or empty");
	}

	/**
	 * Assert that a string has valid text content; that is, it must not be
	 * <code>null</code> and must contain at least one non-whitespace character.
	 * 
	 * <pre class="code">
	 * Assert.hasText(name, &quot;'name' must not be empty&quot;);
	 * </pre>
	 * 
	 * @param text
	 *            the string to check
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @see StringUtils#hasText
	 */
	public static void hasText(String text, String message) {

		if (!StringUtils.hasText(text)) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that a string has valid text content; that is, it must not be
	 * <code>null</code> and must contain at least one non-whitespace character.
	 * 
	 * <pre class="code">
	 * Assert.hasText(name, &quot;'name' must not be empty&quot;);
	 * </pre>
	 * 
	 * @param text
	 *            the string to check
	 * @see StringUtils#hasText
	 */
	public static void hasText(String text) {

		hasText(text,
				"[Assertion failed] - this String argument must have text; it must not be <code>null</code>, empty, or blank");
	}

	/**
	 * Assert that the given text does not contain the given substring.
	 * 
	 * <pre class="code">
	 * Assert.doesNotContain(name, &quot;rod&quot;, &quot;Name must not contain 'rod'&quot;);
	 * </pre>
	 * 
	 * @param textToSearch
	 *            the text to search
	 * @param substring
	 *            the substring to find within the text
	 * @param message
	 *            the exception message to use if the assertion fails
	 */
	public static void doesNotContain(String textToSearch, String substring,
			String message) {

		if (StringUtils.hasLength(textToSearch)
				&& StringUtils.hasLength(substring)
				&& (textToSearch.indexOf(substring) != -1)) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that the given text does not contain the given substring.
	 * 
	 * <pre class="code">
	 * Assert.doesNotContain(name, &quot;rod&quot;);
	 * </pre>
	 * 
	 * @param textToSearch
	 *            the text to search
	 * @param substring
	 *            the substring to find within the text
	 */
	public static void doesNotContain(String textToSearch, String substring) {

		doesNotContain(textToSearch, substring,
				"[Assertion failed] - this String argument must not contain the substring ["
						+ substring + "]");
	}

	/**
	 * Assert that an array has elements; that is, it must not be
	 * <code>null</code> and must have at least one element.
	 * 
	 * <pre class="code">
	 * Assert.notEmpty(array, &quot;The array must have elements&quot;);
	 * </pre>
	 * 
	 * @param array
	 *            the array to check
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @throws IllegalArgumentException
	 *             if the object array is <code>null</code> or has no elements
	 */
	public static void notEmpty(Object[] array, String message) {

		if (ObjectUtils.isEmpty(array)) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that an array has elements; that is, it must not be
	 * <code>null</code> and must have at least one element.
	 * 
	 * <pre class="code">
	 * Assert.notEmpty(array);
	 * </pre>
	 * 
	 * @param array
	 *            the array to check
	 * @throws IllegalArgumentException
	 *             if the object array is <code>null</code> or has no elements
	 */
	public static void notEmpty(Object[] array) {

		notEmpty(
				array,
				"[Assertion failed] - this array must not be empty: it must contain at least 1 element");
	}

	/**
	 * Assert that a collection has elements; that is, it must not be
	 * <code>null</code> and must have at least one element.
	 * 
	 * <pre class="code">
	 * Assert.notEmpty(collection, &quot;Collection must have elements&quot;);
	 * </pre>
	 * 
	 * @param collection
	 *            the collection to check
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @throws IllegalArgumentException
	 *             if the collection is <code>null</code> or has no elements
	 */
	public static void notEmpty(Collection collection, String message) {

		if (CollectionUtils.isEmpty(collection)) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that a collection has elements; that is, it must not be
	 * <code>null</code> and must have at least one element.
	 * 
	 * <pre class="code">
	 * Assert.notEmpty(collection, &quot;Collection must have elements&quot;);
	 * </pre>
	 * 
	 * @param collection
	 *            the collection to check
	 * @throws IllegalArgumentException
	 *             if the collection is <code>null</code> or has no elements
	 */
	public static void notEmpty(Collection collection) {

		notEmpty(
				collection,
				"[Assertion failed] - this collection must not be empty: it must contain at least 1 element");
	}

	/**
	 * Assert that a Map has entries; that is, it must not be <code>null</code>
	 * and must have at least one entry.
	 * 
	 * <pre class="code">
	 * Assert.notEmpty(map, &quot;Map must have entries&quot;);
	 * </pre>
	 * 
	 * @param map
	 *            the map to check
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @throws IllegalArgumentException
	 *             if the map is <code>null</code> or has no entries
	 */
	public static void notEmpty(Map map, String message) {

		if (CollectionUtils.isEmpty(map)) {

			throw new IllegalArgumentException(message);
		}
	}

	/**
	 * Assert that a Map has entries; that is, it must not be <code>null</code>
	 * and must have at least one entry.
	 * 
	 * <pre class="code">
	 * Assert.notEmpty(map);
	 * </pre>
	 * 
	 * @param map
	 *            the map to check
	 * @throws IllegalArgumentException
	 *             if the map is <code>null</code> or has no entries
	 */
	public static void notEmpty(Map map) {

		notEmpty(
				map,
				"[Assertion failed] - this map must not be empty; it must contain at least one entry");
	}

	/**
	 * Assert that the provided object is an instance of the provided class.
	 * 
	 * <pre class="code">
	 * Assert.instanceOf(Foo.class, foo);
	 * </pre>
	 * 
	 * @param clazz
	 *            the required class
	 * @param obj
	 *            the object to check
	 * @throws IllegalArgumentException
	 *             if the object is not an instance of clazz
	 * @see Class#isInstance
	 */
	public static void isInstanceOf(Class clazz, Object obj) {

		isInstanceOf(clazz, obj, "");
	}

	/**
	 * Assert that the provided object is an instance of the provided class.
	 * 
	 * <pre class="code">
	 * Assert.instanceOf(Foo.class, foo);
	 * </pre>
	 * 
	 * @param type
	 *            the type to check against
	 * @param obj
	 *            the object to check
	 * @param message
	 *            a message which will be prepended to the message produced by
	 *            the function itself, and which may be used to provide context.
	 *            It should normally end in a ": " or ". " so that the function
	 *            generate message looks ok when prepended to it.
	 * @throws IllegalArgumentException
	 *             if the object is not an instance of clazz
	 * @see Class#isInstance
	 */
	public static void isInstanceOf(Class type, Object obj, String message) {

		notNull(type, "Type to check against must not be null");

		if (!type.isInstance(obj)) {

			throw new IllegalArgumentException(message + "Object of class ["
					+ ((obj != null) ? obj.getClass().getName() : "null")
					+ "] must be an instance of " + type);
		}
	}

	/**
	 * Assert that <code>superType.isAssignableFrom(subType)</code> is
	 * <code>true</code>.
	 * 
	 * <pre class="code">
	 * Assert.isAssignable(Number.class, myClass);
	 * </pre>
	 * 
	 * @param superType
	 *            the super type to check
	 * @param subType
	 *            the sub type to check
	 * @throws IllegalArgumentException
	 *             if the classes are not assignable
	 */
	public static void isAssignable(Class superType, Class subType) {

		isAssignable(superType, subType, "");
	}

	/**
	 * Assert that <code>superType.isAssignableFrom(subType)</code> is
	 * <code>true</code>.
	 * 
	 * <pre class="code">
	 * Assert.isAssignable(Number.class, myClass);
	 * </pre>
	 * 
	 * @param superType
	 *            the super type to check against
	 * @param subType
	 *            the sub type to check
	 * @param message
	 *            a message which will be prepended to the message produced by
	 *            the function itself, and which may be used to provide context.
	 *            It should normally end in a ": " or ". " so that the function
	 *            generate message looks ok when prepended to it.
	 * @throws IllegalArgumentException
	 *             if the classes are not assignable
	 */
	public static void isAssignable(Class superType, Class subType,
			String message) {

		notNull(superType, "Type to check against must not be null");

		if ((subType == null) || !superType.isAssignableFrom(subType)) {

			throw new IllegalArgumentException(message + subType
					+ " is not assignable to " + superType);
		}
	}

	/**
	 * Assert a boolean expression, throwing <code>IllegalStateException</code>
	 * if the test result is <code>false</code>. Call isTrue if you wish to
	 * throw IllegalArgumentException on an assertion failure.
	 * 
	 * <pre class="code">
	 * Assert.state(id == null, &quot;The id property must not already be initialized&quot;);
	 * </pre>
	 * 
	 * @param expression
	 *            a boolean expression
	 * @param message
	 *            the exception message to use if the assertion fails
	 * @throws IllegalStateException
	 *             if expression is <code>false</code>
	 */
	public static void state(boolean expression, String message) {

		if (!expression) {

			throw new IllegalStateException(message);
		}
	}

	/**
	 * Assert a boolean expression, throwing {@link IllegalStateException} if
	 * the test result is <code>false</code>.
	 * <p>
	 * Call {@link #isTrue(boolean)} if you wish to throw
	 * {@link IllegalArgumentException} on an assertion failure.
	 * 
	 * <pre class="code">
	 * Assert.state(id == null);
	 * </pre>
	 * 
	 * @param expression
	 *            a boolean expression
	 * @throws IllegalStateException
	 *             if the supplied expression is <code>false</code>
	 */
	public static void state(boolean expression) {

		state(expression,
				"[Assertion failed] - this state invariant must be true");
	}
}